Production of heavy crude oil by heating



Oct. 31, 1967 c, NT ET AL 3,349,846

PRODUCTION OF HEAVY CRUDE OIL BY HEATING Filed July 30, 1964 FUEL & OR AIR PRODUCTION INJECTION HEAVY OIL 32 ZOOTFEI; a M

F/G. 3 i fmi li PRODUCTION F/G. Z

INJECTION STRING OIL STRATUM =7 AQUIFER INVENTORS J.C.TRANTHAM, .LRBRUNS BYHW. HENNIGAN M. R.TEK,

A TTOlP/VE VS United States Patent 3,349,346 PRUDUQTION 0F HEAVY CRUDE GIL BY HEATING Joseph C. Trantham, Henry W. Hennigan, and Michael J. Fetlrovich, Bartlesville, Okla, Mehmet R. Telr, Ann Arbor, Mich, and John R. Bruns, Bartlesvilie, Okla, assignors to Phillips Petroleum Company, a corporation of Delaware Filed July 30, 1964, Ser. No. 386,246 Claims. (Cl. 166--11) This invention relates to a process for producing heavy crude oil of low mobility from a stratum containing the same by a novel method of heating the stratum.

Highly viscous crude oils are found in strata in various areas and these have been extremely diihcult to produce. Such crude oils have such low mobility that heating them with steam or by direct or inverse in situ combustion is practically impossible by ordinary methods. This invention provides a process or method for heating a stratum containing a viscous crude oil, where the stratum overlies an adjacent aquifer, so as to render the crude oil substantially less viscous and more highly mobile thereby causing same to flow into well(s) adjacent the heated area.

Accordingly, it is an object of the invention to provide a process for producing heavy crude oil from a stratum containing the same by heating the oil in the stratum in a novel manner. Another object is to provide a process or method for burning a fuel in an aquifer subjacent a stratum containing the heavy crude oil. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises burning fuel with injected O -containing, combustion-supporting gas in an upper level of an aquifer subjacent a heavy crudebearing stratum thru a well penetrating said stratum and aquifer so as to heat the oil in the overlying stratum, reduce the viscosity thereof, and cause same to flow into said well; and recovering the oil from the well. Air is the usual combustion-supporting gas, but air enriched with 0 or 0 alone, may be used.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing of which FIGURE 1 is an elevation of a single well in a stratum and aquifer showing an arrangement of equipment for performing the invention; FIGURE 2 is an elevation showing a similar arrangement in a pair of spaced-apart wells for effecting a second embodiment of the invention; and FIGURE 3 is an elevation illustrating an arrangement of 3 wells with equipment therein for effecting another embodiment of the invention.

Referring to FIGURE 1 a stratum 10 overlies an aquifer 12, which in turn overlies a shale formation 14. A well 16 passes thru stratum 10 and penetrates aquifer 12 preferably to shale formation 14 and is completed by casing 18 extending to shale formation 14. Casing 18 is perforated Within aquifer 12 at 20 and within stratum 10 at 22. Packer 24 is positioned approximately at the interface of stratum 10 and aquifer 12 around an injection tubing string 26 extending into the aquifer. A production tubing string 28 extends into stratum 10 and is provided with conventional pumping means not shown. A packer 30 is positioned around tubing strings 26 and 23 just above stratum 10. Packer 24 and the lower end of tubing string 26 must be fabricated of high temperature steels or alloys to withstand temperatures of the order of 1800 to 2000 F.

Utilizing the arrangement illustrated in FIGURE 1, either air or a combustible mixture of air and fuel gas is injected thru injection string 26 from any suitable source at ground level so as to displace water in the aquifer and 3,349,845 Patentedl Oct. 31, 1967 pocket of gas 32. If the crude oil in stratum 10 contains suflicient volatile hydrocarbon and the injection air is heated, a combustible mixture is formed without the inclusion of fuel gas in the injection stream. However, in most instances it is desirable and essential to incorporate in the injected air sufficient fuel gas such as natural gas, LPG, propane, etc., to form a combustible mixture. Injection of the combustible mixture into aquifer 12 causes the gas to move into the aquifer thru the more permeable streaks therein and penetrate deep into the aquifer. The injected gas is lighter than water in the aquifer and in due course forms a socalled bubble adjacent the oil stratum as shown at 32. After the gas has concentrated as shown, it is preferable to fill injection string 26 with a non-combustible gas by displacing the combustible mixture with air, CO and nitrogen, or other stable gas. Thereafter, an incendiary device or an electric igniting device is utilized to ignite the gas in the aquifer and burn same out into the aquifer adjacent stratum 10 so as to heat the overlying stratum. This heating causes oil in the heated area to become less viscous so that it flows thru perforations 22 into the casing around the lower end of production string 28. The oil is then readily produced by pumping.

It is preferred to repeat the injection and burning steps so as to expand the heated area in stratum 10 and increase oil temperature therein. This repetition may be continued until further production of oil around well 16 is no longer profitable.

In FIGURE 2 a pair of Wells 18 and 19 extend thru oil stratum 10 and penetrate aquifer 12. The arrangement of equipment in wells 18 and 19 is similar to that shown in well 18 of FIGURE 1, injection string 26 and produc: tion string 28 being positioned in well 18 and injection string 27 and production string 29 being shOWn in well 19.

In operating with the arrangement of FIGURE 2 the air-gas mixture is injected thru tubing string 26 while maintaining well 19 open to flow but under substantial backpressure. As the injection proceeds, the injected gas moves into aquifer 12 and displaces water toward well 19. The displaced water is preferably produced from well 19 thru tubing string 27 until the combustible gaseous mixture reaches well 19 and forms pocket or bubble 32. The injection is continued until the gaseous mixture is detected in the tubing string 27 at the well head. Thereafter, air is injected into tubing string 27 so as to force the combustible gas therein to the bottom of the well. An incendiary device or other igniting means is then applied to the bubble 32 at the bottom of well 19 as by dropping the ignited incendiary device down tubing string 27. The device ignites the combustible gas in well 19 below the lower packer and effects burning of the gas in pocket 32 into the aquifer along the bottom of stratum 10. After burning is initiated, it is also feasible to resume injection of combustible gaseous mixture thru tubing string 26 so as to feed the combustion zone advancing toward well 18 from well 19 thru gas bubble or pocket 32. The burning procedure heats the oil in stratum 10 intermediate wells 18 and 19 so as to reduce the viscosity and greatly increase the mobility thereof. This results in oil flowing into wells 18 and 19 above the lower packers from which it is readily produced thru production strings 28 and 29. It is helpful in this type of operation to maintain substantial backpressure on the vent Well so as to increase the size of the gas pocket or bubble 32. Backpressures in the range of 50 p.s.i.g. to 2000 p.s.i.g. are preferable.

When the combustion zone has passed from well 19 to well 18, another combustion zone may be moved thru the aquifer in the same manner, or injection of the combustible gaseous mixture may be reversed by injecting thru tubing string 27 to form another gas pocketextendform a large bubble or ing between wells and igniting the gaseous mixture below packer 24 in the manner used in igniting the gaseous mixture below the lower packer in well 19, after which injection thru tubing string 27 is resumed to move the combustion zone thru the aquifer in the reverse direction. This reversal may be repeated until further production becomes unprofitable.

In FIGURE 3 wells 40, 42, and 44 pass thru stratum into aquifer 12 in the same manner as the wells in FIG- URES 1 and 2.. Wells 40 and 42 are equipped similarly to Well 16 of FIGURE 1, being provided with upper and lower packers 30 and 24, respectively, and with tubing string 46 in each well extending below packer 24 and tubing strings 48 in each well extending into stratum 10 between the packers. Well 44 is equipped with a production string 50 extending into stratum 10.

One method of operating with the arrangement illustrated in FIGURE 3 comprises injecting fuel gas thru tubing string 46 in well 40 and injecting air thru tubing string 46 in well 42 While maintaining well 44 under substantial backpressure. Injection of the fuel gas and air thru the 2 wells should be regulated so that the separate gases arrive at well 44 as near simultaneously as possible. When a combustible gaseous mixture appears in tubing string 50 at the Well head, injection thru wells 40 and 42 is terminated and the combustible mixture is displaced from tubing string 50 by injection of air into same. The combustible mixture in the bottom of well 44 is ignited in the usual manner and the combustion continues with resumption of injection of fuel gas thru well 40 and air thru well 42 as before. The combustion at the bottom of well 44 beats the adjacent stratum and produces oil in the bottom of well 44. The oil is produced from well 44 in conven tional manner.

A preferred method of operating utilizing the arrangement of FIGURE 3 comprises injecting a combustible mixture of fuel gas and air thru each of wells 40 and 42, utilizing tubing strings 46 to deliver the mixture below packers 24. The injected gas is forced into the aquifer and forms a gas pocket extending from each of the injection wells to well 44. After the production of combustible mixture is sensed in tubing string 50 at the well head, air is used to displace the combustible mixture from the tubing string and ignition of the combustible mixture at the bottom of well 44 is effected as described hereinbefore. Here again, a substantial backpressure is maintained on the gas in well 44 and injection of the mixture thru each of wells 40 and 42 is resumed after ignition. In this manner, a combustion zone moves thru the aquifer radially outwardly from well 44 toward each of wells 40 and 42, thereby heating the overlying stratum and the oil therein so as to produce heated oil in all 3 wells in the pattern. It is also feasible to omit the resumption of injection of the combustible mixture and allow the combustible zone to move at its own rate into the aquifer, but it is preferred to resume injection since a greater amount of heating is effected by this procedure.

Well 44 may represent a central well in a ring of surrounding wells in a 5, 7, or 9 spot pattern conventional in the art, with wells 40 and 42 representing ring wells. Wells 40, 42, and 44 may also represent three parallel lines of wells, each well in the lines being operated as described in connection with the wells of FIGURE 3. Likewise, in FIGURE 2 wells 18 and 19 may represent wells in 2 parallel lines of wells, each of which is operated in accordance with wells 18 and 19.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

We claim:

1. A process for producing oil from a viscous oil-bearing stratum wherein the mobility of the oil is low and said stratum overlies an adjacent aquifer, which comprises the steps of;

(1) drilling a well thru said stratum into said aquifer;

(2) forming a combustible mixture of air and fuel only in said aquifer around said well;

(3) burning said mixture only in said aquifer so as to heat the oil in the adjacent oil-bearing stratum and reduce the viscosity thereof thereby effecting flow of the heated oil into said well; and

(4) recovering the oil from said well.

2. The process of claim 1 wherein the air of step (2) is injected thru said well into the adjacent aquifer.

3. The process of claim 1 wherein a second well is drilled into said aquifer and the air of step (2) is injected thru said second well into the aquifer and passes therethru to the area around first said well for the burning in step (3).

4. The precess of claim 3 wherein a fuel gas is injected thru a third well passing thru said stratum into said aquifer and thru the intervening aquifer to said area to form a combustible mixture with the injected air.

5. A process for producing oil from a viscous oil-bearing stratum wherein the mobility of the oil is low and said stratum overlies an adjacent aquifer, which comprises the steps of:

(1) drilling a well thru said stratum into said aquifer;

(2) injecting a combustible mixture of O -containing gas and fuel gas only into the aquifer around said well adjacent said stratum to form a substantial volume of said mixture therein;

(3) igniting the mixture in said aquifer adjacent said well and burning same only within said aquifer so as to heat the oil in the overlying stratum thereby reducing the viscosity thereof and causing the heated oil to flow into said well; and

(4) producing the oil of step (3) from the well.

6. The process of claim 5 further comprising:

(5) repeating step (2) after burning has ceased;

(6) repeating step (3) following step (5); and

(7) producing additional oil caused to flow into said well by steps (5) and (6).

7. A process for producing oil from a viscous oil-bearing stratum wherein the mobility of the oil is low, said stratum overlies an adjacent aquifer, and said stratum and aquifer are penetrated by first, second, and third wells, said second well being intermediate the outer wells, comprising the steps of:

(1) injecting a fuel gas only into said aquifer thru said first well;

(2) injecting air only into said aquifer thru said third well;

(3) continuing steps (1) and (3) with said second well open to flow so as to provide a combustible mixture of air and fuel only in said aquifer adjacent said second well;

(4) igniting and burning the mixture of step (3) while continuing steps (1) and (2) for a substantial period of time so as to heat and cause oil in the above stratum to flow into said second well;

(5) following step (4) switching injection of fuel gas to said third well and injection of air to said first well so as to form a combustible mixture only in said aquifer adjacent said stratum extending outwardly from said second well;

(6) igniting and burning the mixture of step (5) so as to heat and cause additional oil in the above stratum to flow into said second well; and

(7) recovering oil from said second well produced by the foregoing steps.

8. A process for producing oil from a viscous oil-bearing strautm wherein the mobility of the oil is low, said stratum overlies an adjacent aquifer, and said stratum and aquifer are penetrated by first, second, and third wells, said second well being intermediate the other wells, comprising the steps of (1) injecting a combustible mixture of air and fuel gas only into said aquifer thru each of said first and third wells so as to provide a mass of said mixture extending thru said aquifer from said first and third Wells to said second Well;

(2) thereafter, igniting said mixture adjacent said sec ond well and burning same in said aquifer back toward said first and third Wells so as to heat the oil in the adjacent stratum and cause same to flow into said wells; and

(3) recovering oil from said (1) and (2).

9. The process of claim 8 including the steps of:

(4) continuing injection in step (1) during the burning of step (2)so as to effect slow propagation of burnzones toward said first and third wells thereby increasing the heating and flow of oil into said wells.

10. A process for producing oil from a stratum containing viscous oil of low mobility overlying an adjacent aquifer, which comprises the steps of:

(1) providing (a) a well extending thru said stratum into said aquifer,

(b) ,a first tubing string extending into said aquifer,

(c) a packer on said first string closing the resulting annulus adjacent the interface of said stratum and said aquifer, and

wells produced by steps (d) a second tubing string extending to a level jus above said packer having a pump thereon; (2) injecting a combustible mixture of air and fuel thrt said first tubing string into said aquifer;

(3) burning said mixture in said aquifer so as to heat the adjacent stratum and render the oil therein readily fiowable, causing same to fiow into said Well above said packer; and

(4) pumping the oil resulting from the foregoing steps from said well.

References Cited UNITED CHARLES E. OCONNELL, Primary Examiner.

S. I. NOVOSAD, Assistant Examiner. 

1. A PROCESS FOR PRODUCING OIL FROM A VISCOUS OIL-BEARING STRATUM WHEREIN THE MOBILITY OF THE OIL IS LOW AND SAID STRATUM OVERLIES AN ADJACENT AQUIFER, WHICH COMPRISES THE STEPS OF: (1) DRILLING A WELL THRU SAID STRATUM INTO SAID AQUIFER; (2) FORMING A COMBUSTIBLE MIXTURE OF AIR AND FUEL ONLY IN SAID AQUIFER AROUND SAID WELL; (3) BURNING SAID MIXTURE ONLY IN SAID AQUIFER SO AS TO HEAT THE OIL IN THE ADJACENT OIL-BEARING STRATUM AND REDUCE THE VISCOSITY THEREOF EFFECTING FLOW OF THE HEATED OIL INTO SAID WELL; AND (4) RECOVERING THE OIL FROM SAID WELL. 